Canola is an important oil crop. Canola oil is considered to be a superior edible oil due to its low levels of saturated fatty acids. “Canola” refers to rapeseed (Brassica spp.) that has an erucic acid (C22:1) content of at most 2 percent by weight (compared to the total fatty acid content of a seed) and that produces (after crushing) an air-dried meal containing less than 30 micromoles (μmol) of glucosinolates per gram of defatted (oil-free) meal. These types of rapeseed are distinguished by their edibility in comparison to more traditional varieties of the species.
Regular canola oil (extracted from natural and earlier commercial varieties of rapeseed) is relatively high (8%-10%) in α-linolenic acid content (C18:3) (ALA). This fatty acid is unstable and easily oxidized during cooking, which in turn creates off-flavors of the oil. It also develops off odors and rancid flavors during storage.
It is known that reducing the α-linolenic content level by hydrogenation increases the oxidative stability of the oil. Hydrogenation is routinely used to reduce the polyunsaturates content of vegetable oils. The food industry has used hydrogenation to raise the melting point of vegetable oils, leading to the creation of oil-based products with textures similar to butter, lard and tallow. During hydrogenation, trans isomers of unsaturated fatty acids are commonly produced. However, the nutritional properties of trans fatty acids mimic saturated fatty acids, thereby reducing the overall desirability of hydrogenated oils.
The development of NATREON (a trademark of Dow AgroSciences) oil has created an even healthier canola oil and increased the oxidative stability of the oil. NEXERA seeds are related. NATREON canola oil typically has over 70% oleic acid (C18:1) and less than 3% linolenic acid (C18:3). The dietary effects of high oleic and low linolenic have been shown to have dramatic effects on health by lowering the low-density lipoproteins (LDL) and have little or no adverse effects in the high-density lipoproteins. LDLs mediate the deposition of cholesterol on blood vessels leading to artherosclerosis and coronary heart disease. U.S. Pat. No. 6,489,543 (SV095-08); U.S. Pat. No. 6,433,254 (Nex 705); U.S. Pat. No. 6,455,763 (S010); and U.S. Pat. No. 6,444,879 (1709) relate to agronomically superior high oleic canola varieties. U.S. Pat. Nos. 5,965,755 and 6,169,190 (AG019) relate to high oleic, low linolenic acid canola oil.
Although rapeseed meal is relatively high in protein, its high fiber content decreases its digestibility and its value as an animal feed. Compared to soybean meal, regular canola meal contains higher values of dietary fiber. Because of its high dietary fiber, canola meal has about 20% less metabolizable energy (ME) than soybean meal. As a result, the value of the meal has remained low relative to other oilseed meals such as soybean meal. Rakow (2004a) reports that canola meal is sold for about 60-70% of the price of soybean meal mainly because of the high fiber content of canola meal (about 12% crude fiber) compared to soybean meal (about 4% crude fiber), which reduces its feed value particularly in rations for pigs and poultry. Canola meal contains approximately 36-38% crude protein whereas soybean meal contains 48% on an as-is basis. Also, the presence of glucosinolates decreases the value of some canola meal due to the deleterious effects these compounds have on the growth and reproduction of livestock.
In canola, most genetic selection to date has been focused on oil content and agronomic characteristics. The improvement of meal quality in Brassica napus canola must focus on increasing the metabolizable energy (ME) content of the meal in order to make it more competitive with other high protein feed such as soybean meal in rations for monogastric animals. Reduction in fiber levels would increase the nutritive value of canola meal by elevating the ratio of protein and ME.
Canola with yellow seed coats have been found to have thinner hulls and thus less fiber and more oil and protein than varieties with dark color seed coats. Seed coat color is generally divided into two main classes, yellow or black (or dark brown), although varying shades of these colors, such as reddish brown and yellowish brown, are also observed. Seedcoat color in rapeseed may be different depending on the particular species and variety of Brassica. Yellow-seeded rapeseed varieties are common in Asian countries, and in China, there is an abundance of yellow-seeded cultivars in production, particularly in B. juncea and B. rapa varieties.
Stringam et al. (1974) reported that yellow seeds of B. rapa had higher oil, higher protein, and lower fiber content than brown seeds. Bell & Shires (1982) studied the composition of yellow and brown canola seed hulls and compared their digestibility by pigs. The brown hulls contained more fiber and lignin. Shirzadegan & Robbelen (1985) reported an average of 2.6% higher oil and protein content in brown versus black seeds, and a 3% reduction in fiber and hull contents of yellow and brown seeds compared to common black seeded forms.
Bell (1995) noted that canola meal had high nutritional quality but the presence of hulls in the meal reduced the levels of available energy and protein, as well as amino acids and minerals. The nutritional value of canola meal can be improved by reducing fiber and/or hull contents, leading to greater digestibility of available protein and amino acids. The development of yellow-seeded varieties with less hull is offered as a possibility to increase the feed value of canola meal.
Simbaya et al. (1995) compared yellow-seeded meals from B. napus, B. juncea, and B. rapa to brown-seeded canola. On average, yellow-seeded samples had higher protein and lower dietary fiber (and lignin).
Getinet & Rakow (1997) studied the inheritance patterns of seed coat pigmentation repression in B. carinata. Slominski et al. (1999) compared the nutritive value for broiler chickens fed meals derived from these lines/varieties.
For more than 20 years, Agriculture and Agri-Food Canada (AAFC)-Saskatoon has conducted research towards the development of yellow-seeded B. napus and has produced different sources of yellow-seeded B. napus germplasm (Rashid et al. 1994; Rashid & Rakow 1995; Rakow et al. 1999 a & b; and Relf-Eckstein et al. 2003), the latter of which compares YN97-262 and three other yellow seeded lines to 46A65.
Rashid et al. (1994) relates to an interspecific crossing scheme used to develop yellow-seeded B. napus (with traits such as improved fertility). Rakow et al. (1999a) notes that in B. napus, no yellow-seeded types occur naturally; all have been developed through inter-specific hybridizations with B. napus, B. juncea, and B. rapa in various crossing combinations. Early lines had lower oil content than black seed lines (attributed to poor embryo development), were low yielding, and highly susceptible to blackleg (Leptosphaeria maculans). Rakow et al. (1999b) relates to a “much needed” new source of yellow-seeded B. napus, which was developed from interspecific crosses between black-seeded WESTAR and yellow-seeded B. juncea and B. carinata. The yellow-seeded lines thus obtained were reported to have low erucic acid, low glucosinolates, 60-65% oleic acid, 18-20% linoleic acid, and 7-9% linolenic acid.
Rakow (2004b) reports that yellow-seeded Brassica oil seeds have significantly reduced meal fiber levels and increased seed oil content, as compared to black or brown-seeded forms. This reference discusses results of a December 2003 report where yellow-seeded line YN01-429 was compared to black-seeded 46A65. The results are as follows:
TABLE 1YN01-42946A65Yield (kg/ha)16401520Color (WIE*)−46.61.9Seed Oil %47.8643.88Meal Protein %52.5554.27Seed Weight (g/1000s)3.332.79glucosinolates (umol/g)11.114.1TSAT %6.586.91C22:10.0160.021Blackleg (% Westar)5315ADF % meal9.6215.69ADL % meal1.827.36(*color was measured by method E313, white index)
This reference also reports of an increasing demand for high oleic/low linolenic acid, heat-stable, low trans fatty acid vegetable oils for frying applications. This reference reports of a desire to reduce fiber content and glucosinolate content to enhance the overall nutritional value of canola meal to meet an increasing demand for plant-based, high protein meal sources for the feed industry. This reference further reports that germplasm lines with low total saturated fat content (4.5-5.0%), low total glucosinolate content (<3 μmoles/gram of seed), high seed weight (>3 gram/100 seeds) and disease resistance have been developed in yellow-seeded forms of B. napus, and that future goals include continuing to increase such gene pools, and increasing meal protein content and seed size.
Rakow & Raney (2003) notes that rapeseed (canola) oil is high in oleic acid and essential polyunsaturated fatty acids, and that further oil quality improvements would include the development of very high oleic acid/low linolenic acid (HOLL) varieties for use in frying applications, and the creation of low and very low (zero) saturated fat oils. According to this reference, meal quality improvements will focus on fiber reductions (especially lignin) through the creation of yellow-seeded B. napus forms. Reduction or elimination of glucosinolates is listed as a further breeding goal. This reference further notes that new Brassica oil seed crops, such as B. juncea and B. carinata, are under development, but it is noted that each species has specific seed oil and meal quality challenges that need to be addressed, including modification of fatty acid compositions to improve oil quality.
Improved oil levels and protein levels are primary objectives of rapeseed breeding programs. Thus, introduction of a yellow seed coat trait into canola varieties is desirable, in the interest of providing improvements in both the seed oil and protein levels. However, integration of genes controlling seed pigmentation from related Brassica species into valuable oilseed Brassica varieties, such as canola varieties, is complicated by the fact that multiple recessive alleles are involved in the inheritance of yellow seed coats in presently available yellow seeded lines. Pod curling is also a common problem due to poor chromosome pairing when yellow-seed color is introgressed from other Brassica species, such as juncea and carinata. 
U.S. Pat. Nos. 6,547,711 and 6,380,466 relate to rapeseed having a yellow-seed coat controlled by a single locus mutation. EP 1 031 577 relates to a Brassica plant transformed with a transparent seed coat gene.
The development, and potential advantages, of yellow-seeded canola combined with having certain advantageous oil profiles has not heretofore been achieved.